LeetCode "Design Twitter"

A mix of hashmap, list and heap.

struct Tw
{
    Tw(long long pts, int tid)
    {
        ts = pts;
        tweetid = tid;
    }
    long long ts;
    int tweetid;
};
struct Cmp
{
    bool operator()(const Tw &a, const Tw &b)
    {
        return a.ts > b.ts;
    }
};
class Twitter {
    long long ts;
    unordered_map<int, unordered_set<int>> fllw;
    unordered_map<int, list<Tw>> twts;
public:
    /** Initialize your data structure here. */
    Twitter() {
        ts = 0;
    }
    
    /** Compose a new tweet. */
    void postTweet(int userId, int tweetId) {
        twts[userId].push_back({ts ++, tweetId});
        if(twts[userId].size() > 10) twts[userId].pop_front();
    }
    
    /** Retrieve the 10 most recent tweet ids in the user's news feed. Each item in the news feed must be posted by users who the user followed or by the user herself. Tweets must be ordered from most recent to least recent. */
    vector<int> getNewsFeed(int userId) {
        priority_queue<Tw, vector<Tw>, Cmp> q;
        for(auto uid : fllw[userId])
        {
            for(auto &tw : twts[uid])
            {
                q.push(tw);
                if(q.size() > 10) q.pop();
            }
        }
        for(Tw &tw : twts[userId])
        {
            q.push(tw);
            if(q.size() > 10) q.pop();
        }
            
        vector<int> ret;
        while(!q.empty())
        {
            ret.push_back(q.top().tweetid);
            q.pop();
        }
        reverse(ret.begin(), ret.end());
        return ret;
    }
    
    /** Follower follows a followee. If the operation is invalid, it should be a no-op. */
    void follow(int followerId, int followeeId) {
        if (followerId != followeeId)
            fllw[followerId].insert(followeeId);
    }
    
    /** Follower unfollows a followee. If the operation is invalid, it should be a no-op. */
    void unfollow(int followerId, int followeeId) {
        fllw[followerId].erase(followeeId);
    }
};